


For Want of Love

by Im_The_Doctor (Bofur1)



Category: Undertale (Video Game), underswap
Genre: Alternate Universe - Underswap (Undertale), Anger, Angst, Angst with a Happy Ending, Babybones (Undertale), Bittersweet, Brother Feels, Brotherly Angst, Child Neglect, Crying, Desperation, Father-Son Relationship, Frustration, Guilt, Hope, Hopeful Ending, Hurt/Comfort, Jealousy, Kid Fic, Loneliness, Major Illness, Medical Conditions, Near Death, Near Death Experiences, Neglect, New Sibling, Papyrus Has 1 HP (Undertale), Regret, Sans (Undertale) Needs a Hug, Sick Papyrus (Undertale), Stress, Weak Soul, Whump
Language: English
Status: Completed
Published: 2021-02-18
Updated: 2021-02-18
Packaged: 2021-03-13 20:14:57
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,804
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29531814
Author URL: https://archiveofourown.org/users/Bofur1/pseuds/Im_The_Doctor
Summary: When Sans heard that he was going to be a big brother, he was absolutely thrilled. Of course, that was before the new sibling stole everyone's attention and affection from him.
Relationships: Papyrus & Sans (Undertale), W. D. Gaster & Papyrus & Sans
Kudos: 71





	For Want of Love

**Author's Note:**

> If you want an extra dash of angst while you read this, put on the song "I Want You Here" by Plumb after the mid-story line break.

When Sans had first been informed that he was going to be a big brother, he was nothing short of _thrilled_. With another child in the lab, all of the adults would realize just how mature and helpful Sans could be.

No longer would he be the one told that he was “too little” for important jobs! At long last he would be the one to fetch Gaster’s steaming, sweet-smelling drinks, without being babied and told that he could have burned himself. He would be the one to stay up late, get more sweets, grow into cool new clothes—and naturally his new sibling would have no choice but to admire him for all the things he could teach them! He had so many secrets to share about the world.

They would be a sort of…personal assistant, he decided, to prove how cool and independent he could be. With the new arrival being small and silly and inexperienced, Sans could win the trust, thanks, praise and affection he deserved. Not to mention that with them around, he would have someone to play with when the adults were too busy with boring science things.

Of course, that was before Sans had realized that his new sibling _was_ one of their boring science things. The day that his dad had given him permission to see the little one, he had practically flown into the lab, eager to introduce himself as the more magnificent sibling who would show them how it was done.

It was rather anticlimactic to introduce oneself to a squishy, discolored cluster of half-formed bones floating in a tube.

Was that really what Sans had looked like once? He was forced to fight off an uncertain scowl at the thought. Given that he couldn’t remember ever looking this gross and helpless, he could only conclude that he had come into the world with all the necessary components right away, walking and talking and—well, actually having a proper _face_. His sibling was the anomalous one. Even its soul looked odd, nothing but a fist-sized lump that shimmered weakly amidst the bubbles.

Everything changed when he reached out to knock on the glass. Before his knuckles could make contact, a sharp smack to the dorsum swatted him away.

“Did I give you permission to touch?” Gaster reproached. “Look with your eye sockets, not your hands.”

“ _Ow_ , Papa!” Sans protested, more startled and offended than hurt as he clutched his hand protectively to his chest.

“Don’t disturb the maturation chamber.”

That would only be the first of the many scoldings he received in the coming days, not just from his father but from the other adults Sans had once assumed to be his friends. His plan of becoming the one they could rely upon was backfiring splendidly; no matter how he tried to offer his help, it went wrong.

“Sans, we can’t get this done with you underfoot.”

“Please, go play somewhere else.”

“Sans, we really don’t have the time.”

“Hey, put that down! It isn’t a toy!”

“Not now, Sans, we’re very busy.”

“Ask someone else.”

“Quiet down!”

“Don’t you have other ways to occupy yourself?”

“Shut the door behind you!”

It would have been hurtful enough if that was all they said, but whenever he managed to duck into the lab unnoticed or he got scooted to the corner out of their way, he couldn’t help but overhear all of the remarks they made about his new sibling. “ _Fascinating_ ,” they called it. “Intriguing. A breakthrough, a wonder of science.”

How could it be? Sans wondered irritably as he was steered out of the lab yet again. The lump of bone in the chamber didn’t even do anything special! A few days ago, the only will it could muster was to twitch a few malformed fingers and all of the doctors rushed about making notes and breathing sighs of delight and relief. Some of them had even _applauded_ the little thing and it didn’t even have a full mouth to smile or thank them.

Whatever happened to the days when Sans would get a pat on the skull for pushing the door open on his own, or the times the lab assistants would cup his cheekbones and coo over his starry eyes and sparkling smile? He couldn’t remember the last time any of them had smiled back. These days they were all stressed and skittish and snappish with him and even with each other from time to time, but they treated his sibling as if it was spun from glass.

In his free time (which he had quite a lot of, now that nobody wanted to acknowledge his existence) Sans had taught himself how to perform a cartwheel. It was much more impressive than whatever the lump was doing, he fumed as he thumped his forehead against the empty breakroom’s observation window.

Maybe he wouldn’t tell any of them that he’d learned—not even Gaster. Maybe he would keep it to himself until he could do two or three cartwheels in a row so that when he eventually demonstrated, they would see how much of his coolness they had missed out on.

His eyelights burned faintly at the notion that followed. Maybe they still wouldn’t care, even if he did tell them. There was no telling when they would have time for him again.

The lump had even taken bedtimes from him. Sans had gotten to stay up later, just as he’d wished, but in his soul he knew it was only because Gaster had forgotten that he needed to be put to bed. One night he had peeked into the lab once to see his father slumped over in front of his sibling’s chamber, skull bowed wearily against folded hands.

Sans couldn’t quite tell if he was asleep or simply thinking so he had crept in quietly, hoping to request a proper tucking in and a bedtime story.

Stumbling in the darkness and knocking over a pile of folders on the nearby chair was a sorry way to get his attention. Gaster had startled and lunged out of his chair in an instant, eyelights flaring.

“Sans! What are you doing in here? You—Oh, now look what you’ve done! Those took us weeks to chart and file and you’ve—”

“I-It was an accident! I’m sorry, Papa, I just—I wanted—” he stammered, huddling down to scoop up the nearest fallen papers. Gaster had sighed harshly as he approached, kneeling across from him.

“Never mind, never mind. I’ll take care of this,” he groused, a trifle less sharply, but Sans could still see the frustration lurking under his dark-rimmed sockets. “It’s late, isn’t it? Shouldn’t you be in bed?”

“I just…” Sans had gulped as he watched him. Gaster’s attention wasn’t on him; he was peering down at the scattered notes, muttering to himself. Shoulders slumping, Sans had crept away and let him be. All he cared about was clearing away the mess.

If Sans had nightmares that night, he would never admit it. Gaster hadn’t been at breakfast to inquire of him anyway.

With an exasperated whine Sans thumped his fists against the window for good measure, earning a few pointed glances from the scientists within who were distracted by the noise.

That didn’t matter. What mattered was the chamber where his sibling sat in the spotlight and did _nothing_ exciting. It was a little bigger now but the more it grew, the uglier it seemed. Couldn’t they see how wrong it looked, limp and reedy and angular? Its soul still hadn’t changed a bit, a misshapen, twisted flicker of fragile light with half a dozen tubes latched onto it. Why the tubes were there, Sans didn’t know, but they didn’t make it any more flattering.

Jaw set, Sans glowered at it, hoping it could sense it through the glass.

“You’re stupid,” he muttered. “You’re stupid and horrible and I don’t want you anymore. It’s your fault everyone’s been so mean to me. Why can’t you just go away so everything can be how it was before?”

* * *

His sibling was sick.

His sibling was _very, very_ sick.

His sibling was…

Sans had startled out of a fitful sleep to the distant sound of alarms ringing and his father’s booming voice. When he scurried from his room and to the lab entryway to find out what the problem was, he had discovered them all clustered around the chamber—the normal state of affairs these days, he mused with a fleeting huff—but the frantic flurry of snatching hands and scrambling feet was unusual. Once he registered the bare, open panic on his father’s haggard face, he knew something was truly wrong.

“Papa?” he called out fearfully as he gripped the doorframe, going unheard as one of the assistants piped up urgently:

“0.9 percent, sir!”

Gaster spat a curse that made Sans flinch in disbelief, but he didn’t have time to vie for his attention again. Another alarm began to wail as the bones in the chamber began to lurch and judder to and fro. It was the most Sans had ever seen them move, but nobody was applauding anymore. It seemed to strike the fear of stars into them; everyone began hollering over each other.

Beyond the blaring of the monitors, it was hard to make out everything they were saying, and even then most of it was scientific chatter that he couldn’t understand. All he heard were snatches of “integrity,” “HP” and “still dropping.” When strung together, that alone was more than enough to make his eye sockets go empty and his knees fall weak.

“Sans? Kid, you can’t be in here! You gotta stay back while we get him stabilized!” someone had commanded as they barged past him, shoving him away with a weighty hand. “Don’t look! You don’t need to see this!”

The door slammed, muffling the chaos within, but it didn’t matter now. What he had seen and heard already was enough. Trembling, Sans backed away until he hit another wall, his head reeling. He knew what HP was; it kept monsters alive. It spurred on the beat that he felt under his soft nightshirt right now, drumming faster and faster.

If his sibling’s HP was “dropping,” wouldn’t that mean…?

 _Oh, no. Oh, no, no, no_.

On legs that would barely support him, he made his way back to the window, eye sockets huge as he watched his father— _their_ father struggle with foreign tools to coax a spark back into the sputtering soul in the chamber. Sans’ own soul threatened to drop out of his ribs when he made note of the chalky discoloration in the maturation fluid. Dust was leaking from his sibling’s deformed marrow.

He had vaguely heard of what happened when monsters died but seeing that, here, now—yet despite the older monster’s warning at the door, he couldn’t tear his stunned gaze away.

 _Stay back while we get him stabilized_.

“ _Him_.”

Sans’ vision blurred at the realization. He had a brother.

That was his little brother down there, leaking real-life _dust_ , with their stoic father sparing real-life tears over him even as he barked orders at the others to help. His brother, who hadn’t yet gotten _any_ chance to touch his feet to the ground, smile, eat sweets, do three cartwheels or be tucked in at bedtime. If Gaster and the others couldn’t light up his soul again, he might never, ever…Oh, _stars_.

Choking on a violent sob that came without warning, guilt and horror burning down his cheeks, Sans flung himself against the glass, the same glass where he’d said those awful things. He had done something truly _evil_ ; he could see that now. Out of nothing but anger and jealousy, Sans had cursed him. He was _killing_ him now with his cruelty!

“I’m sorry! Brother, stop it, please! I’m sorry!”

Everything happening right now was his fault; his brother was only doing what he had said. Sans hadn’t felt wanted because of him; now he’d made that little soul feel the very same. He was only a baby. How was he to cope? His will was too weak; that kind of pain was too much for him to bear!

“I didn’t mean it like this; I didn’t want to hurt you!”

Was he listening anymore? Could he hear through all of the sirens and the shouting? Could the _dust_ listen? When Gaster sparked his soul again, it jumped, heaving with tiny sparks of green healing magic before guttering to gray. Sans moaned at the sight, tears smudging the windowpane.

“No, no, don’t do it…Please, don’t go! This isn’t fair! Light up again, _please_. I want you to stay! I-I’ll share everything with you! I don’t need it all to myself, I need you too! Papa needs you! We’ll love you, I promise! We want you here!”

_I want you here._

_I didn’t mean it._

_I’m sorry._

_I’ll love you, if I get the chance._

_Please._

_Please._

_Please._

Somewhere along the line he dropped gracelessly to the floor. His tears blinded him to whatever was happening down there—and regardless, he could no longer bear to look for the moment the little soul shattered. He hid his face against the carpet, trying to smother the terror away.

It was Gaster who eventually woke him with a hand against his cheekbone. His fingers were shaky with exhaustion but he persisted. “Sans? Are you alright?” he croaked, thumbing at the old tearstains he found on his cheeks. He wasn’t certain how much Sans had seen, but after Gaster had been treated to the full, harrowing experience, he needed some contact with his elder son.

Gradually Sans stirred, foggy eyelights swimming into view. As soon as he registered his father’s presence, he tensed and trembled, fresh moisture rimming his sockets.

“My…b-brother,” he hiccupped miserably. He didn’t want to face whatever unknown these next few minutes held. “I love him, Papa, I swear I do. I don’t want him to go…”

A bitter taste filled Gaster’s mouth. Sans had seen more than he should have, then. Futilely Gaster had prayed that his boy had slept through the emergency, peaceful, innocent and unaware. With a wavering sigh he bent further down, gathering Sans up against him. His soul sank at the whimper Sans let out, face buried against the soft jumper that replaced his stained lab coat. His small hands dug into Gaster’s ribs, clinging as if to make sure he was real.

When was the last time Gaster had held him? In the anxiety and stress of these last several weeks, he could never seem to find the time.

“He’s stable,” he murmured, repeating it once more to convince himself. “Your brother is stable, Sans. He’s alive.” Wordlessly Sans sobbed and shook his head, clearly unbelieving as Gaster nodded toward the window. “Look. You can see for yourself.”

“He…There was dust everywhere,” he murmured pitifully. “His soul wouldn’t glow…”

“I wouldn’t lie to you, son, not about this. Look at him.”

Patiently, motionlessly, he endured the several seconds it took for Sans to summon his courage and turn his head toward the glass. His breath hitched.

Amidst tubes—more than a dozen now—and a trail of bubbles, a fist-sized lump glimmered, casting soft, amber-tinged shadows on the floor around its chamber. For how much grief and effort it had taken to claw its essence back to the living world, it now looked strangely peaceful. Perhaps he was sleeping.

“…He’s not sick anymore?”

Gaster’s shoulders slumped at that, though he did his best to keep his tone neutral. “I’m afraid he’s been rather fragile since he was conceived. I can’t pinpoint why. It’s simply the way he manifested. We’ll need to take very good care of him in the days to come.”

“We?” Sans’ head lifted. “I can help?”

“Once he’s old enough to leave the maturation chamber, your help will probably be the most vital for him. In part, you will be responsible for his experience of this world. He will need your guidance. He’ll need your spirit and your strength to lean on every day.”

A few beats of silence passed as Sans processed this, eyes fixed on the delicate soul. At last he sniffled, wiped his face against his father’s jumper and allowed himself a tiny, tearful laugh. “He’s not blue like I am.”

That wasn’t what Gaster had expected him to say, but he addressed it regardless. “No. Until now, I couldn’t predict the primary color of his magic. I hope that doesn’t disappoint you.”

“Mm-mm…it’s okay. S’good that he’s different. He’s a…a ‘wonder of science.’ Isn’t he?”

“As are you, Sans. With hope, time and care, both of you will live to be truly extraordinary people.”


End file.
